1. Field of the Invention
This invention generally relates to a communication device and communication method.
2. Description of the Related Art
Recently, a high-speed wireless transmission technology has been studied and developed, one of which is a method called UWB (Ultra Wide Band). The UWB utilizes at least 20 percent of fractional bandwidth or at least 500 MHz of ultra high bandwidth. The UWB is a wireless communication method that can realize a high-speed data transmission by sending and receiving data that are spread in an extremely high frequency range, at least 500 MHz.
The UWB communicates with the use of a signal train or signal sequence. An information signal is composed of an impulse signal train that has an extremely short cycle of several hundred picoseconds. An occupied frequency range is extremely wide, as compared to the frequency range that is usually used in a wireless LAN. However, there is a problem in that it is difficult to establish the synchronization of data and a relative signal so as to obtain correlation of data in an impulse radio system, which transmits ultra short pulses without carriers, among radio communication systems of ultra wideband such as the UWB. Japanese Patent Application Publication No. 2003-234691 (hereinafter referred to as Document 1) has been proposed to solve the aforementioned problem as the conventional technique.
The wireless communication system disclosed in Document 1 is equipped with a timing generation device, which transmits a standard pulse signal at certain intervals. A wireless network is established with wireless communication devices, which exist within a range that the standard pulse signal reaches.
The wireless communication system described in Document 1 is equipped with the timing generation device that transmits a standard pulse signal at certain intervals so as to synchronize the standard pulse signal with a transmit and receive circuit. Here, it is to be noted that an additional external device such as the timing generation device is costly.
Besides, there is another problem in that, with the impulse radio system, it is difficult to eliminate the affects caused resulting from noises and also difficult to extract desired signals only, when the signals are received and the data is extracted.